Discharge lamp lighting apparatus

ABSTRACT

A discharge lamp lighting apparatus has a problem that a microcomputer within the apparatus falls down into malfunction due to noises generated in an inside thereof. With such the structure of the discharge lamp lighting apparatus that an operation of a calculation processing circuit, which is built up with the microcomputer, etc., is stopped through stopping the supply of electric power to the calculation processing circuit or bringing it into a sleep mode, it is possible to protecting it from the malfunction, during a time period when high voltage is generated just after starting of lighting of the discharge lamp. Also, with applying a protection processing by means of the calculation processing circuit and also applying an analog protection circuit, in common with, thereby it is possible to ensure reliability thereof further.

BACKGROUND OF THE INVENTION

The present invention relates to a discharge lamp lighting apparatus ofa projection-type display, such as, a liquid crystal projector or thelike.

As a light source for a projection-type display, such as, a liquidcrystal projector or the like, is adopted a high-pressure dischargelamp, such as, a metal halide lamp or a high-pressure mercury lamp,etc., for example, due to the reasons that it has high conversionefficiency and a point-like light source can be obtained, easily fromit.

For the purpose of lighting the high-pressured is charge lamp, adischarge lamp is applied for the exclusive use thereof, which suppliesvoltage and current thereto necessary for the lighting.

Further in recent years, as was described in Japanese Patent Laying-OpenNo. Hei 5-74583 (1993) and Japanese Patent Laying-open No. Hei 8-8076(1996), for example, there is proposed a method for controlling thedischarge lamp lighting apparatus with using a microcomputer, in thedischarge lamp lighting apparatus.

BRIEF SUMMARY OF THE INVENTION

However, due to noises generated within the discharge lamp lightingapparatus, there is possibility that the microcomputer causesmalfunction thereof.

Although the Japanese Patent Laying-Open No. Hei 5-74583 (1993)mentioned above discloses therein an inventive idea of calculating out aconsuming electric power with using the microcomputer, thereby keepingthe electric power constant, however no consideration is paid upon suchmalfunction of the microcomputer due to the noises generated therein. Onthe other hand, the Japanese Patent Laying-Open No. Hei 8-8076 (1996)mentioned above discloses therein an inventive idea of continuing thelighting of the lamp even in the case where the microcomputer causes themalfunction thereof, however there is still a problem that it isimpossible to protect the microcomputer from causing or falling into themalfunction due to such the noises generated therein.

Accordingly, for dissolving such the problems mentioned above, accordingto the present invention, an object of the present invention is toprovide a structure for protecting the microcomputer (i.e., acalculation processing circuit) from the malfunction due to thehigh-voltage generation noises, by stopping an electric power supply tothe microcomputer during the time period when the high-voltages isgenerated before and after starting of lighting of the discharge lamp,i.e., where an ill influences of the noises is at the most.

As an effect of the present invention, it is possible to provide adischarge lamp lighting apparatus, being improved in reliabilitythereof.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

Those and other objects, features and advantages of the presentinvention will become more readily apparent from the following detaileddescription when taken in conjunction with the accompanying drawingswherein:

FIG. 1 is a block diagram for showing a first embodiment of thedischarge lamp lighting apparatus, according to the present invention;

FIG. 2 is a waveform view for explaining an output voltage and operationof an electric power source for a calculation processing circuit, from atime when the discharge lamp starts the lighting up to a time when itturns into a stable lighting condition thereof, in the first embodimentof the discharge lamp lighting apparatus, according to the presentinvention;

FIG. 3(A) is a block diagram for explaining the operation of an ON/OFFcircuit of the electric power source for the calculation processingcircuit shown in FIG. 1, and FIG. 3(B) shows the waveforms of signalsthereof;

FIG. 4 is a block diagram for showing a second embodiment of thedischarge lamp lighting apparatus according to the present invention;

FIG. 5 is a block diagram for showing an example of an analogueprotection circuit according to the present invention;

FIG. 6 is a block diagram for showing a third embodiment of thedischarge lamp lighting apparatus according to the present invention;

FIG. 7 is a block diagram for explaining the operation of a dischargevoltage generation circuit shown in FIG. 6;

FIG. 8 is a view for explaining the discharge lamp lighting apparatus,in which the conventional art is applied;

FIG. 9 is a block diagram for showing a fourth embodiment of thedischarge lamp lighting apparatus according to the present invention;

FIG. 10 is a block diagram of a projector, into which the discharge lamplighting apparatus according to the present invention;

FIG. 11 is a block diagram for showing a fifth embodiment of thedischarge lamp lighting apparatus according to the present invention;

FIG. 12 is a timing chart for explaining the operation of the fifthembodiment;

FIG. 13 is a flowchart for explaining the operation of the fifthembodiment;

FIG. 14 is a timing chart for explaining the operation of a sixthembodiment;

FIG. 15 is a flowchart for explaining the operation of the sixthembodiment; and

FIG. 16 is a block diagram for showing a seventh embodiment of thedischarge lamp lighting apparatus according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments according to the present invention will befully explained by referring to the attached drawings.

<Embodiment 1>

FIG. 1 is a block diagram of the first embodiment of the discharge lamplighting apparatus, according to the present invention.

The discharge lamp lighting apparatus is applied into, such as, aprojection-type display shown in FIG. 10 attached, for example.

In this FIG. 10, a reflector 77 and a high-pressure discharge lamp 78builds up a light source for irradiating a light from a rear surface ofa picture display device 76. The light penetrating through the picturedisplay device 76 is projected onto a screen 74 by means of an opticalsystem 75. The picture display device 76, being made up with a liquidcrystal display device, for example, is driven through a picture displaydevice driver circuit 79, therefore a picture of a large-scaled screencan be obtained on the screen 74. The discharge lamp lighting apparatus80 conducts a starting and a lighting control of the high-pressuredischarge lamp 78.

In FIG. 1, a reference numeral 1 depicts an input terminal of a mainelectric power source, 2 a MOS-FET, 3 a diode, 4 a choke coil, 5 acapacitor, 6 and 7 resistors, 8, 9, 10 and 11 MOS-FETs, 12 a resistor,13 a discharge lamp, 14 a lamp-ON input terminal, 15 an electric powersource for a calculation processing circuit, 16 an ON/OFF circuit forthe calculation processing circuit, 17 a calculation processing circuit,18 a thermistor, 19 a PWM controller circuit, 20 an input terminal of anON/OFF signal for the PWM controller circuit 19, 21 an input terminal ofa control voltage for the PWM controller circuit, 22 a drive circuit 1,23 a drive circuit 2, 24 an input terminal of an ON/OFF signal for thedrive circuit 23, 25 an input terminal of the drive circuit 23, 26 aninput terminal 2 of the drive circuit 23, and 27 is a igniter circuit.

The MOS-FET 2, the diode 3, the choke coil 4, the capacitor 5, theresistors 6, 7, and 12, the drive circuit 22, and the PWM controllercircuit 19 build up an electric power controller circuit. The MOS-FETs8, 9, 10 and 11, and the driver 23 build up a current converter circuit.The igniter circuit 27 generates a high-voltage pulse, thereby startingthe high-pressure discharge lamp 13. The calculation processing circuit17, being built up with a microcomputer, for example, detects an outputvoltage through voltages divided by the resistors 6 and 7, and detectsan output current through voltage generating across the resistor 12, andfurther it watches or supervises temperature of the discharge lamplighting circuit by means of the thermistor 18. Also, the calculationprocessing circuit 17 produces a signal for driving the drive circuit 23mentioned above, upon receipt of an input from the lamp-ON inputterminal 14, thereby providing outputs to the input terminals 25 and 26of the drive circuit 23. It also calculates out an output electricpower, upon the basis of a result of the output voltage detection and aresult of the output current detection mentioned above, therebyproviding a restriction or limit voltage to the control voltage inputterminal 21 of the PMW controller circuit 19 motioned above, so that itcontrols the output electric power to be constant. Further, it comparesthose detection results to the limit values LV1, LV2 and LV3, which aredetermined within an inside of the calculation processing circuit 17.Herein, the limit value LV1 is indicative of an output voltage limitvalue, the limit value LV2 an output current limit value, and the limitvalue LV3 an overheat limit value, which is a limit value of thetemperature of the discharge lamp lighting apparatus, respectively. In acase when it comes to be equal to or greater than LV3 in the result ofthe output voltage detection, or when it comes to be equal to or greaterthan LV3 in the result of observation on the thermistor, the calculationprocessing circuit 17 transmits signals to the ON/OFF signal inputterminal 20 of the PWM controller circuit 19 and the ON/OFF signal inputterminal 24 of the drive circuit 23, so that the discharge lamp lightingapparatus stops the operation thereof, or in a case when it comes to beequal to or greater than LV2 in the result of detection of the outputcurrent, it provides a control voltage to the control voltage inputterminal 20 of the PWM controller circuit 19, thereby controlling thePWM controller circuit 19 so that the output current is restricted witha current value which is determined by LV2. The calculation processingcircuit 17 operates upon supply of electric power from the electricpower source 15 for the calculation processing circuit. The electricpower supply of the electric power source 15 for the calculationprocessing circuit is turned ON/OFF by the function of the calculationprocessing circuit ON/OFF circuit 16. The calculation processing circuitON/OFF circuit 16 has a built-in timer therein, and it stops theelectric power supply to the calculation processing circuit from thecalculation processing circuit electric power source 15, during a timeperiod from when the discharge lamp starts the lighting up to when itgenerates a high voltage, after receiving an input from the lamp-ONinput terminal 14 (i.e., t0-t3 in FIG. 2, which will be mentionedlater).

Explanation will be given about the operation of the electric powerON/OFF circuit for the calculation processing circuit shown in FIG. 1,by referring to FIGS. 2 and 3. Herein, FIG. 2 is a timing chart forexplaining an output voltage and the operation of the electric powersource 15 for the calculation processing circuit, from the time when thedischarge lamp lighting apparatus receives an input from the lamp-ONinput terminal 14 up to the time when it comes into a stable lightingcondition thereof. In this FIG. 2, S1 depicts the output voltage of theON/OFF circuit for the calculation processing circuit shown in FIG. 1mentioned above, and S2 the voltage at the lamp-ON input terminal 14,which is also shown in FIG. 1.

Since the lamp 13 does not light, the electric power controller circuitprovides an output of the maximum voltage V3 when a lamp-ON signal isinputted at a time t0. Then, voltage V4, obtained by superposinghigh-voltage pulses supplied from the igniter circuit 27 upon thevoltage V3 mentioned above, is applied across the high-pressuredischarge lamp 13; therefore, the lamp starts the lighting. For thisreason, noises can be generated very easily during this time periodt0-t2, in particular. Then, the output voltage of the ON/OFF circuit 16for the calculation processing circuit is turned OFF, so as to stop thesupply of electric power to the calculation processing circuit 17,thereby protecting the calculation processing circuit 17 from fallingdown into the malfunction thereof. Also, a glow-discharge starts at thetime t1, with high voltage and small current, and further at the timet2, it is shifted into an arc-discharge, with low voltage and largecurrent. Accompanying an increase of temperature of the lamp, the lampvoltage goes up. At a time t3, the output of the ON/OFF circuit 16 forthe calculation processing circuit is turned ON, and then the electricpower is supplied to the calculation processing circuit 17. Therefore,an alternating current (AC) converter circuit starts the operationthereof, and the high-pressure discharge lamp 13 shifts the operationinto an AC lighting mode. Thereafter, the electric power controllercircuit supplies a constant electric power to the high-pressured ischarge lamp through the constant electric power control when it comes toa steady voltage V1 at a time t4.

FIG. 3(A) shows an example of the circuitry structure of the ON/OFFcircuit for the calculation processing circuit shown in FIG. 1 mentionedabove. In this FIG. 3(A), a reference numeral 40 depicts a lamp-ONsignal input terminal, 41 a one-shot circuit, 42 a timer circuit, 43 aNOR circuit, 44 and 45 transistors, 46 an electric power input terminal,47 a resistor, 48 an inverter circuit, 49 an output terminal of ON/OFFcircuit for the calculation processing circuit.

When the lamp-ON signal is inputted onto the lamp-ON input terminal 14shown in FIG. 1 from an outside of the discharge lamp lightingapparatus, the lamp-ON signal is inputted into the lamp-ON signal inputterminal 40 shown in FIG. 3(A), and then an edge of changeover of thelamp-ON signal is detected within the one-shot circuit 41; thereby,generating a rectangular or square waveform signal, being “Hi (high)”for a certain time period (hereinafter, being called by “signal a0”), tobe inputted into the timer circuit 42 and a base of the transistor 44,as shown in FIG. 3(B). The timer circuit 42 starts a reset of the timerwhen it inputs the rectangular waveform signal of the one-shot circuit41 mentioned above, and it outputs a signal changing from “Low” into“Hi” (hereinafter, a “signal a1”) after passing through a certain timeperiod (hereinafter, “ΔT”) from it. Also, into the NOR circuit 43 areinputted the signal a1 and a signal, which is produced by the transistor44 and 45, the electric power inputting terminal 46 and the resistor 47(hereinafter, a “signal a2”). Also, in a case where an output of the NORcircuit 43 is in “Hi”, then the transistor 45 is turned ON, therebylatching the signal a2 into “Low”. Now, assuming that the signal a0 isoutputted from the one-shot circuit 41, the transistor 44 is turned ON,therefore the output of the NOR circuit 43 comes to be “Low” during thetime period when the outputted signal a0 is in “Hi” in the conditionthereof. Also, since the timer circuit 42 is reset-started with thesignal a0, the signal a2 is “Low” in the condition thereof. For thisreason, an output of the NOR circuit 43 comes to be “Hi”, while thesignal a2 is latched into “Low” through turning ON of the transistor 45,thereby bringing into the condition of waiting an input of the signala2. In this instance, the electric power ON/OFF circuit output terminal49 for the calculation processing circuit is switched from “Hi” into“Low”, and it is latched in the condition of stopping the electric powersupply of the electric power source 15 for the calculation processingcircuit to the calculation processing circuit 17. Thereafter, whenpassing through the time period ΔT of the timer within the timer circuit42, the output of the timer circuit, i.e., the signal a1 is switchedfrom “Low” into “Hi”. With this, the output of the NOR circuit 43 isswitched from “Hi” into “Low”, therefore the transistor 45 is turnedinto OFF in the condition thereof; thus, the signal a2 is released fromthe latching to be “Hi” in the condition thereof. Thus, it is in thecondition of waiting an inputting of the signal at the lamp-ON signalinput terminal, next. In this instance, the electric power ON/OFFcircuit output terminal 40 for the calculation processing circuit isreleased from the “Low” latching condition and switched into “Hi”,therefore the electric power supply is re-started or re-opened to thecalculation processing circuit 17 from the electric power source 15 forthe calculation processing circuit. With such the operations mentionedabove, during the time period where the high voltage is generated forthe high-pressure lamp, i.e., the time period ΔT of the timer, it ispossible to stop the electric power supply to the calculation processingcircuit 17 from the electric power source 15 for the calculationprocessing circuit.

According to the present invention, however it is not always necessaryto stop the electric power supply to the calculation processing circuit17, but it is only necessary of stopping the operation of thecalculation processing circuit 17 for a predetermined time period. Forexample, in a case where the calculation processing circuit is made upwith a microcomputer, it is also possible to control the controlterminal of a sleep mode, for brining the microcomputer into the stopcondition, with an aid of the calculation processing circuit ON/OFFcircuit 16.

As a result of this, it is possible to achieve a swift and stablelighting of the high-pressure discharge lamp, irrespective of theconditions and variability thereof, and also due to the fact that theelectric power supply to the calculation processing circuit is stoppedduring the time period t0-t3 (=ΔT) when the high voltage is generated,it is possible to protect the calculation processing circuit 17 from themalfunction thereof due to the noise generations of high-voltage.

EXAMPLE 2

FIG. 4 is a block diagram for showing a second embodiment of thedischarge lamp lighting apparatus, according to the present invention.With the present structure, in which protection of circuitry of thedischarge lamp lighting apparatus is achieved by adopting thecalculation processing circuit 17 and also an analog protection circuit,in common, it is possible to improve up the safety of the discharge lamplighting apparatus, by the function of the analog protection circuit,even if the calculation processing circuit falls into the malfunction.

In this FIG. 4, those reference numerals 1-27 are same to those shownFIG. 1, and a reference numeral depicts an analog over-voltage detectioncircuit (hereinafter, an “OVP circuit”), 51 an analogue over-heatdetection circuit (hereinafter, an “OTP circuit”), 52 an analogprotection circuit (i.e., an OR circuit), 53 an OR circuit, 54 an analogcurrent limit circuit, and 55 a selector, respectively.

The output voltage is detected by means of the OVP circuit 50,temperature of the discharge lamp lighting circuit is watched orobserved by means of the OPT circuit 51, and the output current isdetected by means of the analog current limit 54, respectively. Each ofthe OVP circuit 50, the OPT circuit 51 and the analog current limitcircuit 54 has a limit value LV4, LV 5 or LV 6 in an inside thereof,respectively. The value LV4 is produced within the OVP circuit, and itindicates an output voltage limit value. When the output voltage isequal or greater than the voltage value determined with LV4, a result ofthis is transmitted to the analog protection circuit 52. However, theOVP circuit 50 stops the operation of detection thereof, during the timeperiod t0-t3 in FIG. 2, where the high voltage is generated. Also, LV6is produced within the OPT circuit 51, and it indicates the limit valueof temperature for the discharge lamp lighting apparatus. When thetemperature of the discharge lamp lighting apparatus goes up to be equalor greater than the temperature determined by LV6, a result of this istransmitted to the analog protection circuit 52. Upon receipt of thedetection results of the OVP circuit 50 and the OTP circuit 51, theanalog protection circuit 52 provides an output to the OR circuit 53.The OR circuit 53 takes a logical OR condition among the output signalof the analog protection circuit 52, and the output voltage detectionresult within the calculation processing circuit 17 and the ON/OFFsignal of the PWM controller circuit 19 due to the result of watchingupon the thermistor, and then it transmits a result thereof to theON/OFF signal input terminal of the PWM controller circuit 19, therebystopping the operation of the electric power controller circuit. Thevalue LV5 is produced within the analog current limit circuit 54, and itindicates an output current limit value. When the output current comesto be equal or greater than the current value determined by LV5, acontrol voltage is provided, so that the output current be limitedwithin the current value determined by LV5, and this control voltage isoutputted to the selector 55. The selector 55 compares the output resultof the analog current limit circuit 54 mentioned above and the controlvoltage due to the result of output current detection within thecalculation processing circuit 17, so as to select the lower one betweenthem, and with the voltage selected, the control voltage input terminal21 of the PWM controller circuit is controlled. Thus, setting the limitvalues LV4, LV5 and LV6 of those analog circuits to be a little bithigher than the limit values LV1, LV2 and LV3 of the calculationprocessing circuit 17 enables the calculation processing circuit 17 tofunction with priority, when the calculation processing circuit 17operates normally, and also to bring the analog protection circuit 52and the analog current limit circuit 54 to function under the conditionsimilar to that when the calculation processing circuit operatesnormally, even if the calculation processing circuit falls into themalfunction thereof, thereby obtaining the protection of the dischargelamp lighting apparatus.

Explanation will be given on the operation of the OVP circuit 50, theOPT circuit 51, the analog protection circuit 52 and the OR circuit 53,shown in FIG. 4, by referring to FIG. 5 attached herewith. FIG. 5 is ablock diagram for showing an example of the analog protection circuit,which is built up with the OVP circuit 50, the OPT circuit 51, theanalog protection circuit 52, and the OR circuit 53. In FIG. 5, thereference numerals 20, 50, 51, 52 and 53 are same to those shown in FIG.4, the LV4 and LV6 are the limit values explained in the above. Andwherein, a reference numeral 56 indicates the detection voltage of theoutput voltage, 57 the detection voltage by means of the thermistor 18,while a reference numerals 58 and 59 depict comparators, and also areference numeral 61 indicates an output signal of the results ofcomparisons on the output voltage and the detection result of thethermistor with the limit values LV1 and LV3, which are conducted withinthe calculation processing circuit 17.

The OVP circuit 50 is built up with the comparator 58 and the limitvalue LV4. The comparator 58 compares the detection output 56 of theoutput voltage to the limit value LV4, and it provides the output of“Hi” when the detection output 56 of the output voltage comes to beequal or greater than the limit value LV4. In the similar manner, theOTP circuit 51 is built up with the comparator 59 and the limit valueLV6. The comparator 59 compares the detection voltage 57 by means of thethermistor 18 and the limit value LV6, and it provides an output of “Hi”when the detection voltage 57 by means of the thermistor 18 comes toequal or greater than the limit value LV6. When any one of the outputscomes to be “Hi” between the comparators 58 and 59 due to the functionof the OR circuit 52 inputting the output voltages of the comparators 58and 59, the output thereof (hereinafter, a “signal b1”) is transmittedto the OR circuit 53. To the other input of the OR circuit 53 isinputted an output signal 61 (hereinafter, a “signal b2”), being aresult of comparison between the output and the detection result of thethermistor and the limit values LV1 and the LV3, which are conductedwithin the calculation processing circuit 17. When either one of thesignal b1 or the signal b2 is “Hi” in the condition thereof, the ORcircuit 53 transmits the output thereof to the ON/OFF signal inputterminal 20 of the PWM controller circuit 19, as was explained in FIG. 4mentioned above, thereby stopping the operation of the PWM controllercircuit 19. With such the present structure, when the discharge lamplighting apparatus is in the abnormal condition, and even in a casewhere no abnormal signal b2 is outputted due to the malfunction of thecalculation processing circuit 17, it is possible to stop the operationof the PWM controller circuit 19 by means of the analog protectioncircuit 52.

<Embodiment 3>

FIG. 6 is a block diagram of a third embodiment of the discharge lamplighting apparatus, according to the present invention. With the presentstructure, it is possible to restrict an open-circuit voltage or no-loadvoltage when the discharge lamp is in the open-circuit condition, andalso since more reliable protection can be expected in the dangerouscondition, where the temperature of the discharge lamp lightingapparatus rises up high during the protection operation of the OTPcircuit, therefore it is possible to improve up the safety of thedischarge lamp lighting apparatus.

In this FIG. 6, the reference numerals 1-27 and 50-55 are same to thoseshown in FIG. 2 mentioned above, and wherein a reference numeral 62depicts an open-circuit or no-load voltage limit circuit, 63 a limitelectric power source, 64 as witch means, and 65 a over-heat protectionlatch circuit. The no-load voltage limit circuit 62 has a limit valueLV7 in an inside thereof. The value LV7 is an output voltage limitvalue, but the voltage value determined by LV7 is sufficiently high,comparing to the output voltage generated when the discharge lamp turnson normally. Thus, when comparing the output voltage limit value LV1within the calculation processing circuit 17 and the limit value LV4 ofthe OVP circuit 50, a relationship is established, which can beexpressed by the following equation:LV1<LV4<<LV7The present limit value LV7 is set for restricting the no-load voltagewhen the discharge lamp is in the open-circuit condition. The no-loadvoltage limit circuit 62 turns the switch means 64 ON when the non-loadvoltage is equal or greater than the voltage value determined by LV7, soas to apply the voltage of the limit voltage source 63 to the controlvoltage input terminal of the PWM controller circuit 19, therebycontrolling the PWM controller circuit 19. The over-heat protectionlatch circuit 65 brings the lamp-ON input terminal into the latchcondition while keeping it into the lamp-ON condition, in a case whenthe temperature of the discharge lamp lighting apparatus comes to beequal or greater than the temperature determined with the over-heatprotection limit value LV3 which is produced within the calculationprocessing circuit 17, thereby stopping the operation of the lightingcircuit, and even if the signal of lamp-ON or lamp-OFF signal isinputted onto the lamp-ON input terminal 14 from an outside of thedischarge lamp lighting apparatus, again, it latches the input signalsto the calculation processing circuit 17 and the electric power ON/OFFcircuit 16 for the calculation processing circuit, thereby preventingthe discharge lamp lighting apparatus from being turned on, again. As aresult of adding of those circuits, it is possible to restrict theno-load voltage when the discharge lamp is in the open-circuitcondition, thereby improving the safety when the discharge lamp is inthe open-circuit condition. Also, protecting the lighting apparatus frombeing turned ON, again under the dangerous condition where thetemperature increases within the lighting apparatus, increases up thesafety.

Explanation will be given on the operation of the no-load voltage limitcircuit 62, by referring to FIG. 7. In the circuit structure shown inFIG. 1 and/or FIG. 4, since it is impossible to control the PWMcontroller circuit 19 when the discharge lamp is in the open-circuitcondition where no current flows through, there is a problem that theno-load voltage cannot be controlled. With the circuit shown in FIG. 7,it is possible to dissolve the problem mentioned above. FIG. 7 shows anexample of the circuit structure for achieving the no-load voltage limitcircuit 62. In this FIG. 7, the reference numeral 21 is the same to thatshown in FIG. 6, and a reference numeral 56 depicts the detectionvoltage of the output voltage (i.e., the divided voltage by theresistors 6 and 7), while reference numerals 66, 67, 69, 72 and 73depict resistors, 68 a NPN transistor, 70 an electric power inputterminal, and 71 a PNT transistor.

The NPN transistor 68 is supplied with base current through theresistors 66 and 67. When the voltage of the detection voltage 56 of theoutput voltage goes up so that the NPN transistor 68 is turned ON, theNPN transitor 68 is turned ON, and following to this, the PNP transistor71 (corresponding to the switch means 62 shown in FIG. 6) is turned ON.Also, since the resistor 69 is a resistor provided for protecting thePNP transistor from overflow of the base-current thereof, thereforecollector current is supplied to the NPN transistor 68, the currentvalue of which is determined by the electric power input terminal 70 andthe resistor 69, thereby adjusting the base current of the PNPtransistor 71. When the PNP transistor 71 is turned ON, the voltageproduced by means of the electric power input terminal 70 and theresistors 72 and 73 (corresponding to the limit voltage source 63 shownin FIG. 6) is inputted to the control voltage input terminal 21 of thePMW limit circuit 19. With this, when the output voltage rises up to theminimum voltage value, at which the PNP transistor 68 is turned ONfirst, the output electric power controller circuit is controlled bymeans of the PWM controller circuit 19, thereby controlling the outputvoltage at the minimum voltage value mentioned above. Also, the controlvoltage value can be set at, arbitrarily, depending upon a resistorratio between the resistors R66 and R67. Further, with the outputvoltage when the discharge lamp is in the open-circuit condition, thereis a possibility that it is outputted with fully high voltage, comparingto that in the case when the discharge lamp lights up normally. For thisreason, the output voltage limit value determined by the resistors R66and R67 mentioned above is set at the voltage value, which is higherthan the maximum output voltage value when the discharge lamp lights upnormally, therefore it is possible to control the voltage when thedischarge lamp is in the open-circuit condition, but without giving illinfluences upon the control of the output electric power controllercircuit when the discharge lamp lights up normally.

<Embodiment 4>

FIG. 9 is a view for explaining a fourth embodiment of the dischargelamp lighting apparatus, according to the present invention. The presentembodiment is same to the first embodiment in the structure thereof,wherein a flicker of the discharge lamp is suppressed by the control ofthe calculation processing circuit 17. FIG. 8 is a view for explainingthe flicker suppressing means for the discharge lamp in relation to theconventional art. S3 and S4 in FIG. 8 depict rectangular waveformcontrol voltages, being opposite to each other in the phase, which areoutputted from the calculation processing circuit 17 to the drivecircuit 23 shown in FIG. 1. S5 is a control signal voltage, which isoutputted from the calculation processing circuit 17 to the PWMcontroller circuit 19 shown in FIG. 1. S6 is an output voltage of theoutput electric power controller circuit, and S7 is an output voltage ofthe AC generator circuit. The time period t5 is same to a half cycle ofthe AC generator circuit, and t6 is superposing voltage width. Herein,assuming that a ratio coefficient between t5 and t6 is kt, then thefollowing relationship is established:t6=kt×t5Further, v5 indicats the control voltage value of the PWM controllercircuit 19, and v6 the height of the superposed voltage. Herein,assuming that the ratio coefficient between v5 and v6 is kv, then thefollowing relationship is established:v 6=kv×t 5In the present operation, each of kt and kv has a constant value. Whenthe signal shown by S5 produced from the calculation processing circuit17 is inputted to the PWM controller circuit 19, voltage as high as(v6−v5)/v5=(kv−1) times of the voltage is superposed on the outputvoltage of the output electric power controller circuit, in synchronismwith S5, for the time period t6, thereby generating the voltage shown byS6. If such the output S6 of the output electric power controllercircuit is converted into the AC voltage within the AC controllercircuit, then the voltage as high as (kv−1) times of the voltage issuperposed, in synchronism with S5 and S6, for the time period t6, asshown by S7. As a result of this, the above-mentioned voltage of aconstant amount of superposition is transmitted to the discharge lampthrough the igniter circuit 22, thereby enabling suppression of flickerof the discharge lamp. However, when the output electric power is small,there is still remained a problem that the flicker is generated in thedischarge lamp even if adopting the present structure into the dischargelamp lighting apparatus.

FIG. 9 is the view for explaining the fourth embodiment of the dischargelamp lighting apparatus, according to the present invention. In thisFIG. 9, reference numerals S3-S7, v5, v6, t5 and t6 indicate the samesignals as shown in FIG. 8 mentioned above. However, in the presentstructure, the values of kt and kv are variable depending upon anincrease or decrease of the output electric power. Thus, the larger theoutput electric power, the smaller the values of kt and kv, on thecontrary to this, the smaller the output electric power, the larger thevalues kt and kv. As a result of this, with adjusting the variationvalues of kt and kv, it is possible to suppress the flicker of thedischarge lamp in the case when the output electric power is small,although it comes up to be the problem encountered in the method shownin FIG. 8 mentioned above.

Further, according to the present embodiment, it is possible to adjustthe position (or the phase) of the superposed voltage on the outputvoltage of the AC converter circuit, arbitrarily, through changing asetting value of the calculation processing circuit 17. Also, it isfurther possible to superpose the voltage at an arbitrary phase on theoutput voltage of the AC converter circuit, in the similar manner as wasmentioned above, by bringing an outside sync signal inputted from anoutside of the discharge lamp lighting apparatus and the output voltageof the AC converter circuit into the synchronism with. Moreover, aboutsynchronizing patterns with the outside sync signal, it is also possibleto obtain the synchronization, not only at an rise-up edge portion or ata fall-down edge, but also, at both edges of the rise-up portion and thefall-down portion thereof, in addition thereto.

<Embodiment 5>

Next, the structure of a fifth embodiment according to the presentembodiment is shown in FIG. 11. The feature of the present embodimentlies in a measure made in a light-out sequence of the discharge lampwith an aid of the calculation processing circuit, thereby obtaining along lifetime of the discharge lamp. FIG. 11 is the view for showing thefifth embodiment of the present invention, and wherein the samereference numerals are attached onto the elements or portionscorresponding to those of the first embodiment shown in FIG. 1. Aportion differing from it lies in a low electric power mode terminal 30.Since others are same to those of the first embodiment, the explanationsthereof are omitted herein.

In general, the discharge lamp available in recent years has four (4)conditions: i.e., a light-out mode where the lamp is turned out; anormal electric power mode where it is turned on normally; a lowelectric power mode where it is turned on with suppressing the electricpower lower than that of the normal electric power mode; and an ultralow electric power mode where it is turned on, but reducing the electricpower once, down to be equal or less than 50%, such as, 30% of thenormal electric power mode, for example, and maintaining this, when itis shifted from the normal electric power mode or the low electric powermode into the light-out mode.

The low electric power mode, turning on the lamp with suppressing theelectric power, such as, 80% of the normal electric power mode, forexample, enables the following effects; i.e., suppression of electricpower consumption, a long lifetime of the lamp, and also, since it isalso possible to lowers down a revolution number of a fan for coolingthe lamp, there can be obtain an effect of lowering the noise generationtherefrom.

The ultra low electric power mode, not moving into the electric power “0(zero)” when shifting the lamp from the lighting-up condition into thelighting-out condition directly, but maintaining a small electric poweronce, thereby reducing the deterioration of electrodes thereof,therefore it is said that it enables to contribute the long lifetime ofthe lamp.

However, when shifting from the normal electric power mode or the lowelectric power mode into the ultra low electric, the electric power ischanged from 100% (or 80%) down to 30%, for example, at a moment,therefore there can be considered the deterioration of electrodes due tothis.

Therefore, according to the present embodiment, when shifting from thenormal electric power mode or the low electric power mode into the ultralow electric, there is provided a time period for decreasing theelectric power, gradually. With this, it is possible to obtain a furtherreduction of deterioration of electrodes.

A timing chart for sequences of reducing the electric power is shown inFIG. 12. In this FIG. 12, it starts from a light-out mode, and thenshifting into the normal electric power mode. And, after shifting intothe low electric power mode once, it turns back to the normal electricpower mode. And, when it shifts from the normal electric power mode intothe ultra low electric power mode, the electric power is reduced down,by taking a time period, such as, about several seconds, for example.And, finally, it is shifted into the light-out mode.

The four (4) modes of the lamp is discriminated through a combinationtwo (2) bits, including a lamp ON signal at the lamp-ON terminal 14,which is inputted into the calculation processing circuit 17, and a lowelectric power signal at the low electric power mode terminal 30. Thus,if the combination of the lamp-ON signal and the low electric powersignal is (Low, Low), for example, it can be discriminated that the lampbe in the light-out mode; if it is (Hi, Low), the normal electric powermode; if it is (Hi, Hi), the low electric power mode; and if it is (Low,Hi), the ultra low electric power mode, respectively.

The processing steps for discriminating those four (4) modes mentionedabove are shown in a flowchart of FIG. 13, in the calculation processingcircuit 17, thereby conducting the electric power control as shown inFIG. 12 mentioned above.

In this FIG. 13, first of all, the condition starts from the light-outmode (S1-1). Next, the input mode is discriminated (S1-2), wherein if itis the normal electric power mode or the low electric power mode, theelectric power control is conducted so that the lamp can operate in thatmode (S1-3), on the other hand, if it is other than those, the processturns back to the discrimination of the input mode (S1-2), again. Next,the input mode is discriminated (S1-4) from the condition of (S1-3), andif it is the ultra low electric power mode, after passing through ashift mode (S1-5) for reducing the electric power, gradually, by takinga time period, being equal to or greater than 0.5 second and,preferably, about 3 seconds, for example, the process moves into anultra low electric power mode (S1-7). Next, discriminating the inputmode (S1-8) from the condition of (S1-7), and if it is the light-outmode, the process moves into a light-out mode (S1-9), on the other handif it is other than that, it turns back to the discrimination of inputmode (S1-8), again. Herein, if it is other than the ultra low electricpower mode in the discrimination of input mode of (S1-4), the input modeis discriminated (S1-6), and wherein if it is the light-out mode, theprocess moves into the light-out mode (S1-9), and if it is other thanthat, it turns back to the discrimination of the input mode (S1-2),again. With the processing steps mentioned above, it is possible toconduct the electric power control as shown in FIG. 12 mentioned above.

However, in the shift mode in (S1-5), the electric power may be, notonly reduced down in a linear manner with respect to the time as shownin FIG. 12, but also reduced down non-linearly, and it may be determineddepending upon the characteristics of the discharge lamp to be applied.Also, the shifting time is enough to be several seconds, for example,but it may be adjusted depending upon the characteristics of thedischarge lamp.

<Embodiment 6>

Next, explanation will be given on the operation of a sixth embodiment,according to the present invention, by referring to FIG. 14. The presentembodiment is same to the fifth embodiment in the circuit structurethereof, however it differs from in the operation thereof. An aspectdiffering from lies in the processes when the low electric power mode.

Namely, according to the timing charge shown in FIG. 14, comparing tothat shown in FIG. 12, the completely same operation is carried out upto the time when the process is shifted into the ultra low electricpower mode, however after shifting into the ultra low electric powermode, it turns into the light-out mode, automatically, if the lowelectric power mode signal turns to be “Low” in spite of elapse of “n”seconds, in the operation. This is an operation for protecting when themode control is not normal in the condition thereof, which is suppliedfrom an outside of the discharge lamp lighting apparatus.

The processing steps of the electric power control shown in FIG. 14,conducted within the calculation processing circuit 17, will be shown inthe flowchart shown in FIG. 15.

Those other than the steps S1-10 and S1-11 are same to those shown inFIG. 13, and therefore explanation will be omitted on those portions,herein.

First of all, after turning into the ultra low electric power mode(S1-7), the timer counter is reset and is also started (S1-10), which isprovided within the calculation processing circuit 17. In cases where itis determined to be those other than the light-out mode in the step ofdiscrimination of input mode (S1-8), the process shifts into a step oftimer discrimination (S1-11), thereby turning back to the step ofdiscrimination of input mode (S1-8) when it is determined to be lessthan the predetermined time period (i.e., “n” seconds) by means of thetimer. On the other hand, if it is determined to be equal or greaterthan the predetermined time period (i.e., “n” seconds) by means of thetimer, the step is shifted into the light-out mode (S1-9), andtherefore, it can shift into the light-out mode, automatically, even ifthe input mode is not set to be the light-out mode.

With such the operation as was mentioned above, it is possible to shiftthe step into the light-out mode, automatically, even in the case wherethe combination of the lamp-ON signal and the low electric power signalwill not to be (Low, Low) due to any drawback in the control suppliedfrom an outside of the discharge lamp lighting apparatus, althoughinherently it should be (Low, Low) so that the lamp turns into thelight-out mode after turning into the ultra low electric power mode.

<Embodiment 7>

Next, the structure of a seventh embodiment according to the presentinvention will be shown in FIG. 16. The feature of the presentembodiment lies in that in an outside of the calculation processingcircuit is added a nonvolatile memory for reserving data for use ofvarious settings, and also that the contents of the nonvolatile memorycan be re-written from an outside of the discharge lamp lightingapparatus, thereby improving flexibility of the discharge lamp lightingapparatus.

FIG. 16 is a view for showing the structure of the seventh embodimentaccording to the present invention, wherein the same reference numeralsare attached on the portions or elements corresponding to those of thefifth embodiment showing in FIG. 11. The portion differing from lies inan EEPROM 32 and a TXD 31. Others than those are same to those of thefifth embodiment, and therefore explanation will be omitted thereabout,herein.

The EEPROM 32 carries out reading/writing of data through a serial datatransmission or communication with the calculation processing circuit17, which is made up with two (2) pieces of lines, such as, a data lineand a clock line, for example. For the communication between thecalculation processing circuit 17 and the discharge lamp lightingapparatus, for example, UART (Universal Asynchronous ReceiverTransmitter) is applied, with using the low electric power mode terminal30 to be a serial data receiving terminal (hereinafter, “RXD”) incommon, and further adding a serial data transmitting terminal(hereinafter, “TXD”) 31 thereto.

When writing data into the EEPROM 32 from an outside of the dischargelamp lighting apparatus, the address thereof and data are transmitted tothe calculation processing circuit 17 via the RXD 30. Upon relayingthis, the calculation processing circuit 17 carries out the writingprocess of data of said the address into the EEPROM 32.

When reading out data of the EEPROM 32 from the outside of the dischargelamp lighting apparatus, the address is transmitted via the RXD 30 tothe calculation processing circuit 17. Upon relaying this, thecalculation processing circuit 17 carries out the process of reading outthe data of said the address to the EEPROM 32. When completing theread-out of said the data, the calculation processing circuit 17transmits that data to the outside via the TXD 31.

With such the processes as was mentioned above, it is possible to readand write the contents of the EEPROM 32 from the outside of thedischarge lamp lighting apparatus.

As a result of this, reading out of the various kinds of setting datafrom the EEPROM 32, while storing them within the EEPROM 32, by means ofthe calculation processing circuit 17, just after starting the operationof the discharge lamp lighting apparatus, enable an increase on theflexibility of the discharge lamp lighting apparatus. For example, in acase where it is necessary to drive the discharge lamps 13, each havingdifferent inverter frequency, the calculation processing circuit readsthe values of the inverter frequencies there in from the EEPROM 32, andchanges the value of the inverter frequency within the EEPROM 32 fittingto the discharge lamp 13, thereby it is possible to deal with it,without changing of the circuit thereof.

Although the EEPROM 32 is applied as the nonvolatile memory in thepresent embodiment mentioned above, however it should not be restrictedonly to this, but it is also possible to apply a flash ROM, for example,in the place thereof.

As was mentioned fully in the above, with the discharge lamp lightingapparatus according to the present invention, it is possible to obtainan effect that the calculation processing circuit can be protected fromfalling into the malfunction due to the noises. Also, with using theprotection circuit together with the calculation processing circuit andthe analog circuit in common, controlling the no-load voltage when thedischarge lamp is in the open-circuit condition enables an improvementof the safety thereof. Further, with adding the superpose voltage havingthe width and the height, being in inverse relation to theincrease/decrease of the output electric power, onto the output voltageof the AC converter circuit, it is possible to suppress the flicker ofthe discharge lamp.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential feature or characteristicsthereof. The present embodiment(s) is/are therefore to be considered inall respects as illustrative and not restrictive, the scope of theinvention being indicated by the appended claims rather than by theforgoing description and range of equivalency of the claims aretherefore to be embraces therein.

1. A discharge lamp lighting apparatus, comprising: an output electricpower controlling circuit; an alternating current converting circuitwhich converts an output of said output electric power controllingcircuit into an alternating current; an igniter circuit which amplifiesan output of said alternating current converting circuit; an outputvoltage detecting unit which detects an output voltage of said outputelectric power controlling circuit; a driving current detecting unitwhich detects a discharge lamp driving current; a calculation processingcircuit which controls said output electric power controlling circuitdepending upon detection results from said output voltage detecting unitand said driving current detecting unit; and an electric power sourcewhich supplies electric power to said calculation processing circuit,wherein operation of said calculation processing circuit is stopped atleast during a time period when high voltage is generated just afterstarting upon lighting of a discharge lamp.
 2. The discharge lamplighting apparatus, as described in the claim 1, wherein the supply ofelectric power is stopped to said calculation processing circuit atleast during the time period when the high voltage is generated justafter starting the lighting of said discharge lamp, whereby stopping theoperation of said calculation processing circuit.
 3. The discharge lamplighting apparatus, as described in the claim 1, wherein saidcalculation processing circuit is built up with a microcomputer, andsaid microcomputer is brought into a sleep mode, at least during thetime period when the high voltage is generated just after starting thelighting of said discharge lamp.
 4. A discharge lamp lighting apparatus,comprising: an output electric power controlling circuit; an alternatingcurrent converting circuit which converts an output of said outputelectric power controlling circuit into an alternating current; anigniter circuit which amplifies an output of said alternating currentconverting circuit; an output voltage detecting unit which detects anoutput voltage of said output electric power controlling circuit; adriving current detecting unit which detects a discharge lamp drivingcurrent; a calculation processing circuit which controls said outputelectric power controlling circuit depending upon detection results fromsaid output voltage detecting unit and said driving current detectingunit; and an electric power source which supplies electric power to saidcalculation processing circuit; an analog protection circuit whichcontrols operation of said discharge lamp lighting apparatus upon basisof the detection result of said output voltage detecting unit; and anoutput current limit circuit for making such control that an outputcurrent of said discharge lamp is limited upon basis of the result ofsaid driving current detecting unit, wherein said output electric powercontrolling circuit is controlled by said calculation processing circuitupon basis of the detection result of said output voltage detecting unitand the detection result of said driving current detecting unit, andalso said output electric power controlling circuit is controlled bysaid analog protection circuit and said output current limit circuit. 5.The discharge lamp lighting apparatus, as described in the claim 1,further comprising: an analog protection circuit which controlsoperation of said discharge lamp lighting apparatus upon basis of thedetection result of said output voltage detecting unit; and an outputcurrent limit circuit which makes such control that an output current ofsaid discharge lamp is limited upon basis of the result of said drivingcurrent detecting unit, wherein said output electric power controllingcircuit is controlled by said calculation processing circuit upon basisof the detection result of said output voltage detecting unit and thedetection result of said driving current detecting unit, and also saidoutput electric power controlling circuit is controlled by said analogprotection circuit and said output current limit circuit.
 6. Thedischarge lamp lighting apparatus, as described in the claim 1, furthercomprising: an output current limit circuit, whereby controlling saidoutput voltage to be equal to or less than a predetermined value uponbasis of the detection result of said output voltage detection unit. 7.The discharge lamp lighting apparatus, as described in the claim 1,further comprising: a thermistor for use of detecting temperature,wherein supply of the electric power to said discharge lamp is stoppedwhen said thermistor detects the temperature to be equal to or greaterthan a predetermined value, and also the stoppage of the electric powerto said discharge lamp continues up to a time when a main electric poweris cut off once.
 8. The discharge lamp lighting apparatus, as describedin the claim 1, wherein a superpose voltage is added on at least eitherone of a front end portion and a rear end portion of a rectangularwaveform output of said alternating current converting circuit, havingat least one of width and level of said rectangular waveform output,being increased as the output electric power comes to be small.
 9. Thedischarge lamp lighting apparatus, as described in the claim 1, whereinwhen the discharge lamp is shifted from a discharge lamp drive conditioninto a lamp light-out condition, it passes through an ultra low electricpower drive condition of driving the discharge lamp with an ultra lowelectric power, being equal to or less than 50% of that when it isdriven normally; and a period for shifting from said discharge lampdrive condition into said ultra low electric power drive condition isequal to or less than 0.5 second.
 10. The discharge lamp lightingapparatus, as described in the claim 9, wherein the discharge lamp isshifted into the lamp light-out condition after said ultra low electricpower drive condition passes through a predetermined time period. 11.The discharge lamp lighting apparatus, as described in the claim 1,further comprising: a nonvolatile memory, wherein write-in and read-outof setting data into said nonvolatile memory is controlled from an outside of said discharge lamp lighting apparatus via said calculationprocessing circuit.
 12. The discharge lamp lighting apparatus, asdescribed in the claim 4, further comprising: an output current limitcircuit, whereby controlling said output voltage to be equal to or lessthan a predetermined value upon basis of the detection result of saidoutput voltage detection unit.
 13. The discharge lamp lightingapparatus, as described in the claim 4, further comprising: a thermistorfor use of detecting temperature, wherein supply of the electric powerto said discharge lamp is stopped when said thermistor detects thetemperature to be equal to or greater than a predetermined value, andalso the stoppage of the electric power to said discharge lamp continuesup to a time when a main electric power is cut off once.
 14. Thedischarge lamp lighting apparatus, as described in the claim 4, whereina superpose voltage is added on at least either one of a front endportion and a rear end portion of a rectangular waveform output of saidalternating current converting circuit, having at least one of width andlevel of said rectangular waveform output, being increased as the outputelectric power comes to be small.
 15. The discharge lamp lightingapparatus, as described in the claim 4, wherein when the discharge lampis shifted from a discharge lamp drive condition into a lamp light-outcondition, it passes through an ultra low electric power drive conditionof driving the discharge lamp with an ultra low electric power, beingequal to or less than 50% of that when it is driven normally; and aperiod for shifting from said discharge lamp drive condition into saidultra low electric power drive condition is equal to or less than 0.5second.
 16. The discharge lamp lighting apparatus, as described in theclaim 4, further comprising: a nonvolatile memory, wherein write-in andread-out of setting data into said nonvolatile memory is controlled froman outside of said discharge lamp lighting apparatus via saidcalculation processing circuit.